This invention relates to a grain drying and conditioning apparatus of the type which includes a pair of spaced air previous walls confining a generally vertical column of grain, the innermost of the walls defining a plenum chamber, and the plenum chamber being divided into upper and lower air flow sections by a plenum divider. More particularly, this invention is directed to an improved grain drying and conditioning apparatus which includes a passageway for foreign particulate matter to travel from the upper section of the plenum chamber into a portion of the grain column adjacent the lower section of the plenum chamber.
Grain drying and conditioning apparatus are generally used to dry large quantities of grain. Such apparatus are often designed to operate in a continuous manner. Grain is fed into a top portion of the grain dryer and gradually flows down the grain column until it is removed by a suitable conveyor system adjacent a bottom of the grain dryer. Treated (heated) air is passed through the grain column so that the grain is heated and dried while it passes through a portion of the grain column adjacent the upper section of the plenum chamber and is cooled while it passes through a portion of the grain column adjacent the lower section of the plenum chamber.
During this process, foreign particulate matter from the grain, such as bee wings, fines cracks, shells and dirt collects on surfaces in the upper section of the plenum chamber. The collection of these materials reduces the efficiency of the grain dryer and presents a fire hazard. Accordingly, the upper section of the plenum chamber must be cleaned periodically to maintain the efficiency of the grain dryer and to prevent the occurrence of a fire.
In order to clean the upper section of the plenum chamber the operator must first shut down the grain dryer. The operator must then wait until the upper section has cooled to a temperature sufficient to permit a person to enter the plenum chamber. The operator then enters the chamber to sweep and collect the debris from the plenum chamber. After the upper section has been cleaned, the drier must be turned on and heated to a sufficient temperature to continue drying the grain.
The cleaning process of the plenum chamber divider is inefficient and expensive. The grain dryer must be shut down for periods of up to three hours. In addition, a large amount of thermal energy is wasted simply because the plenum chamber must be cooled down and then heated up again for every cleaning event. These expenses are usually quite large because a grain dryer operating under normal conditions requires cleaning at least once a day to maintain efficient operating parameters and to avoid becoming a fire hazard.
The cleaning process also exposes the operator to a variety of dangerous conditions. The upper section is very large and often relatively dark. Therefore, the operator must use a scaffolding and lighting system to reach most of the surfaces that require cleaning. The operator is also exposed to a large amount of foreign matter in the air during the sweeping and cleaning process. Therefore, the operator must wear protective clothing (including a breathing mask) to prevent the inhalation of the foreign matter (all within a relatively warm, enclosed space).
The primary purpose of such apparatus is to remove moisture from the grain and thus prevent mildew and spoilage. The apparatus is not necessarily designed to remove foreign matter from the grain and, in fact, that is an undesirable side effect of conditioning the grain. Grain transactions are typically conducted on a weight basis, so it is preferred that any foreign matter which is initially in the grain stay within the grain, at least through the drying and conditioning process. According, it would be advantageous to provide a means for removing foreign particulate matter which collects in the upper section of the plenum chamber and placing the foreign particulate matter back into the grain column without disrupting the continuous operation of the grain drier.
The handling of foreign matter in a grain dryer has been addressed by the prior art. For example, Zimmermann, U.S. Pat. No. 3,896,562, shows a grain conditioning apparatus which includes two concentric annular previous walls spaced to confine a grain column, and to form a plenum chamber. A blower and heater assembly is mounted within the plenum chamber. A baffle means is provided to separate the plenum chamber into positive and negative pressure zones. An annular slot permits solid material in the positive pressure zone to pass from the positive pressure zone to the negative pressure zone. The solid material is then drawn into the intake of the blower and heater assembly where it is purportedly consumed. If the foreign material is not completely consumed on the first pass, it is intended that it continue to pass through the burner until it is consumed and turned to fine ash. Thus, the solid material is not returned to the grain column, thereby reducing the total weight of the grain exiting the grain dryer.
Ausherman, U.S. Pat. No. 3,474,903, discloses a grain drying apparatus which includes a pair of conduits extending transversely of the dryer and through the side walls to convey combustible debris therefrom. Heated combustion gases act to discharge the inflammable debris and the like from the plenum chamber. Thus, the conduits discharge the debris into the atmosphere and do not return any of that material back into the grain column.
Sime, U.S. Pat. No. 4,914,834, shows an apparatus that reintroduces into a grain column fines and other debris collected outside an outermost pervious wall of the grain column. However, Sime does not show or teach a method or means to remove fines or other debris that can collect within the plenum chamber.